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Procalcitonin levels should not guide CAP diagnosis, treatment
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Serum procalcitonin levels do not have sufficient sensitivity or specificity to distinguish bacterial from viral community-acquired pneumonia, according to new study findings published in Clinical Infectious Diseases.
According to the researchers, the complex etiology of community-acquired pneumonia (CAP) makes disease management difficult. CAP can be caused by both bacteria and viruses, but the treatment of bacterial pneumonia differs from that of viral pneumonia.
“In cases of bacterial pneumonia, initial antibiotic treatment is important for infection resolution, and a shorter time between diagnosis and treatment improves prognosis,” Ishan S. Kamat, MD, MBA, internal medicine resident at Baylor College of Medicine, and colleagues wrote. “However, because of the diverse etiologies and the limitations of extant diagnostic techniques, empiric antibiotic therapy is standardly recommended for all adults with CAP, and the clinician finds him/herself with the conundrum of having to select recommended antibiotics vs. avoiding unnecessary ones.”
It has been thought that procalcitonin serum levels increase during a bacterial pneumonia infection, but many studies supporting this theory were performed among pediatric patients “in whom etiologies have not been well established and/or adults who have a variety of respiratory disorders.” Despite this, the FDA approved the use of procalcitonin to “guide initiation and duration of antibiotic treatment in suspected lower respiratory tract infections,” and the test is widely used in hospitals in the United States, according to the study.
Kamat and colleagues conducted a meta-analysis of 12 studies focused on serum procalcitonin levels among a total of 2,408 adult patients with CAP whose infection had an established etiology.
They reported that serum procalcitonin had a 0.55 sensitivity (95% CI, 0.37-0.71) and 0.76 specificity (95% CI, 0.62-0.86).
The findings suggest that serum procalcitonin levels are “unlikely” to distinguish bacterial from viral pneumonia, and that procalcitonin levels do not provide “reliable evidence” for providing or withholding antibiotic treatment.
“The sensitivity and specificity are both too low and variable for the results to be confidently used in the decision-making process,” Kamat and colleagues wrote.
The researchers recommended future prospective trials assessing the diagnostic ability of procalcitonin in cases in which the etiology is already known, but that type of research would be challenging.
“The problem inherent in this approach is that, because of the difficulties in determining the etiology of CAP, the number of patients that can be included will be severely restricted, and one will not know how representative that population might be,” Kamat and colleagues wrote. – by Marley Ghizzone
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Leah Molloy, PharmD
CAP can be caused by either viruses or bacteria, and the physician’s ability to reliably differentiate between pathogens carries significant implications for antimicrobial stewardship. The value of procalcitonin, a peptide reported to be elevated in bacterial but not viral infections, as such a diagnostic tool continues to be debated. The meta-analysis by Kamat and colleagues suggests that it is insufficient to differentiate between bacterial and nonbacterial pneumonia. The 12 studies included were thoughtfully selected to include only patients for whom a clear diagnosis and etiology were available. Unlike manufacturer-proposed algorithms associating procalcitonin concentrations greater than 0.25 µg/L with bacterial infections, this analysis used a higher threshold of 0.5 µg/L, but noted consistently poor performance across a range of values. Because atypical bacteria are associated with lower procalcitonin concentrations than typical bacteria, including both may have reduced the performance of the test compared with differentiating viruses from typical bacteria only. However, the prevalence of both types of bacteria in CAP dictate that a clinically useful test must be able to differentiate either type from viruses, a measure that was not achieved in the studies reviewed. Future research may better define the role of procalcitonin, perhaps as a measure of illness severity.
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